This invention relates to security protection apparatus used for example to detect the approach of an intruder to certain specified items or to detect the movement of the items from a chosen orientation or position.
The items may be objects or articles such as paintings or jewellery, machines of every type including office equipment, motor cars, industrial machinery and the like.
It has been noted that the observed devices in the security field, such as reed relays, mercury switches, vibrating reed and the like do not meet the desirable requirements of simplicity of construction and operation, sensitivity, accuracy and stability over periods of time and under varying temperatures.
An object of the present invention is to provide continuous movement sensing and further objects are that the initial stage of electronic circuit switching, whilst being extremely sensitive, is thoroughly reliable in repetitive operation requiring no mechanical setting or resetting, no deterioration in switching contacts, is not inhibited by changing ambient temperature. A further object is to provide a range of sensitivities which may be automatically operable according to the environment requirements and particularly enabling increased sensitivity at night.
A further object is that the movement sensor device be very small so as to be able to be positioned on small articles. Further objects are that the sensor require a minimum of skill to set up, the sensor be completely autonomous and self-contained, be adaptable to many security situations, the sensor enable a large measure of automation in its manufacture, and be cheap to produce.